Solid-state photodiode imaging device and method of manufacturing the same

ABSTRACT

According to one embodiment, a solid-state imaging device includes: a photodiode which is provided in a pixel region in which each pixel in a pixel forming region above a substrate is disposed; an interconnection layer which includes interconnections to connect the photodiode to peripheral circuits and an interlayer insulating film to insulate the interconnections from each other, and is provided above the photodiode; a color filter which is provided above the interconnection layer corresponding to the pixel region, and limits a wavelength of light incident on the photodiode. A light incident position correcting layer is provided between the color filter corresponding to the pixel disposed in at least the outer peripheral portion of the pixel forming region and the interconnection layer, and includes an anti-reflection film which is provided above the interconnection layer, and materials which have a negative refraction index and provided above the anti-reflection film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2012-183449, filed on Aug. 22, 2012; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments disclosed herein relate generally to a solid-state imagingelement, a solid-state imaging device and a method of manufacturing thesame.

BACKGROUND

A defect-introduced solid-state imaging device is proposed in therelated art, which is provided with a multi-layered interconnectionlayer and a microlens above a semiconductor substrate on which alight-receiving element is formed for every pixel region. In thesolid-state imaging device, photonic crystals are disposed to guidelight to the light-receiving element between the multi-layeredinterconnection layer and the microlens to improve a light condensingefficiency of the light-receiving element.

In addition, pixels of the existing CMOS (ComplementaryMetal-Oxide-Semiconductor) image sensors are being further shrunk, andwith this an F value decreases in order to make resolution high.Therefore, a distance between a sensor chip IC (Integrated Circuit) anda camera lens tends to be shorter and shorter. As a result, lightcondensing loss such as shading occurs on the peripheral portion ofsensor pixels due to light incident thereon with an inclination, so thatthe sensitivity of the image quality and the like are degraded. Forexample, in case of a pixel disposed near the outer peripheral portionamong the pixels two-dimensionally disposed above the semiconductorsubstrate, the incident light with an inclination passed through themicrolens does not reach the light-receiving element of thecorresponding pixel but is guided along an optical path to be mixed inan adjacent pixel. Therefore, a light-harvesting property is declined.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating aconfiguration of a solid-state imaging device according to a firstembodiment.

FIGS. 2A and 2B are diagrams schematically illustrating refractionpatterns of light in a material.

FIG. 3 is a top view schematically illustrating an exemplary structureof photonic crystals used in the first embodiment.

FIGS. 4A and 4B are diagrams illustrating an example of a region inwhich the photonic crystals are arranged.

FIG. 5 is a diagram illustrating an example of a method of disposing thephotonic crystals in a pixel forming region.

FIGS. 6A to 6C are diagrams illustrating calculation results of opticalsimulations in which an optical path of the photonic crystals having anegative refraction index is simulated.

FIGS. 7A to 7C are diagrams schematically illustrating an operation ofthe solid-state imaging device according to the embodiment.

FIGS. 8A to 8F are cross-sectional views schematically illustrating anexample of procedures performed in a method of manufacturing thesolid-state imaging device according to the first embodiment.

FIG. 9 is a top view of FIG. 8B.

FIGS. 10A to 10H are cross-sectional views illustrating an example ofprocedures performed in a method of manufacturing a solid-state imagingdevice according to a second embodiment.

FIG. 11 is a top view of FIG. 10B.

FIGS. 12A to 12C are cross-sectional views schematically illustrating anexample of procedures performed in a method of manufacturing thesolid-state imaging device in a case where a low refraction indexmaterial is the air.

DETAILED DESCRIPTION

In general, according to one embodiment, there is provided a solid-stateimaging device including a photodiode, an interconnection layer which isprovided above the photodiode, a filter, a light incident positioncorrecting layer. The photodiode is provided in a pixel region in whicheach of a plurality of pixels is disposed, and the pixels are formed ina pixel forming region above a substrate in a matrix shape. Theinterconnection layer includes interconnections to connect thephotodiode to peripheral circuits formed above the substrate and aninterlayer insulating film to insulate the interconnections from eachother. The filter is provided above the interconnection layercorresponding to each pixel region to limit a wavelength of the lightincident on the photodiode. The light incident position correcting layeris provided between the filter corresponding to the pixel disposed in atleast the outer peripheral portion of the pixel forming region and theinterconnection layer. Further, the light incident position correctinglayer includes an anti-reflection film which is provided above theinterconnection layer and materials which have a negative refractionindex and provided above the anti-reflection film.

A solid-state imaging element, a solid-state imaging device, and amethod of manufacturing the same according to embodiments will bedescribed in detail with reference to the accompanying drawings hereinbelow. Further, the invention is not limited to the embodiments. Inaddition, the cross-sectional views of the solid-state imaging deviceused in the following embodiments are schematically illustrated, so thatrelations between thicknesses and widths of layers, and thickness ratiosand the like of the respective layers may be different from the actualones. Furthermore, the film thicknesses to be described below areprovided as examples, and the invention is not limited thereto.

First Embodiment

FIG. 1 is a cross-sectional view schematically illustrating aconfiguration of a solid-state imaging device according to a firstembodiment. The solid-state imaging device, for example, is a CMOSsensor. The solid-state imaging device is provided with: a pixel formingportion 10 in which pixels are formed, the pixel including aphotoelectric conversion element and an element reading a signal fromthe photoelectric conversion element; an interconnection layer 20 inwhich interconnections are formed to be connected to the element formedin the pixel forming portion 10; a protection film 51 which protects theupper portion of the interconnection layer 20; a color filter 31 whichlimits a wavelength of light incident on each pixel of the pixel formingportion 10; and a microlens 32 which is provided for each pixel.

The pixel forming portion 10 is configured of a substrate 11 such as apredetermined conductive type of single-crystal silicon substrate inwhich the pixels are formed in a matrix shape. In each of pixel regionsR_(p) of the substrate 11 which are partitioned by pixel separatingportions (not illustrated), a photodiode 12 is provided as thephotoelectric conversion element which detects incident light passingthrough the microlens 32 and the color filter 31. Each photodiode 12corresponds to a pixel. The light beams received by the respectivephotodiodes 12 are different in wavelength from each other due to theoperation of the color filter 31. In addition to the above components,the pixel region R_(p) is provided with a read transistor (notillustrated) which reads an electrical level of charges accumulated inthe photodiode 12 and the like.

Further, in a peripheral circuit region (not illustrated) above thesubstrate 11, transistors which constitute a signal processing circuitwhich processes electrical signals (pixel signals) converted and outputby the photodiode 12, a driving control circuit for controlling theoutput of the pixel signals through the driving of the photodiode 12,and the like are formed.

The interconnection layer 20 includes interconnections 21 and interlayerinsulating films 22 and 23. The interconnections 21 are provided toelectrically connect the photodiode 12 and the peripheral circuits,which may be formed by one or plural layers. In addition, theconnections between the interconnections 21 or between theinterconnections 21 and the elements formed in the substrate 11 are madethrough via holes or contact holes which are not illustrated. Examplesof the materials of the interconnection 21 may include metal such asaluminum, copper, titanium, molybdenum, and tungsten or silicide such asTiSi, MoSi, and WSi. In this way, the interconnections 21 serve as lightshields made of a metallic material and thus are provided at positionswhere the light incident on a light-receiving region of the photodiode12 is not blocked.

The interlayer insulating films 22 and 23 are provided for electricalinsulation for the interconnections 21 and the interconnections 21,between the substrate 11 and the lowermost interconnection 21, andbetween the uppermost interconnection 21 and the color filter 31. Forexample, silicon oxide may be used as the interlayer insulating films 22and 23.

The protection film 51 is a film which is provided in a lower layer ofthe color filter 31 in terms of the manufacturing process such that thetop face of the interlayer insulating film 23 becomes flush with theprotection film 51 at positions where a light incident positioncorrecting layer 40 to be described below is formed. For example, asilicon oxide film or a silicon nitride film may be used as theprotection film 51.

The color filter 31 is provided above the photodiode 12 to transmitlight in a specific wavelength band toward the photodiode 12. Ingeneral, for example, three pixels constitute a picture element, and thecolor filters 31 of red (R), green (G), and blue (B) each are providedfor the pixels in the picture element. Note that, this configuration ispresented as an example, and the color filters 31 of other colors may beused in which the number of the color filters 31 in one picture elementhas no limitation. In addition, while not illustrated in the drawing,the picture elements are two-dimensionally disposed above the substrate11 in a predetermined cycle.

The microlens 32 is provided on the color filter 31 in each pixel regionR_(p) to condense the light into the pixel region R_(p).

The solid-state imaging device according to the embodiment is configuredto dispose the light incident position correcting layer 40, which servesto make the position of the emitted light move to the incidentdirection, between the color filter 31 and the interconnection layer 20(the interlayer insulating film 22) in at least the pixel disposed atthe outer peripheral of a pixel forming region R in which the pixels aretwo-dimensionally formed. The light incident position correcting layer40 is configured such that an anti-reflection film 41, photonic crystals42 having a negative refraction index, and an anti-reflection film 43are stacked on the interlayer insulating film 22.

The anti-reflection film 41 is provided between the photonic crystals 42and the interlayer insulating film 22 to prevent the reflection of theincident light. In addition, the anti-reflection film 43 is providedbetween the color filter 31 and the photonic crystals 42 to prevent thereflection of the incident light. However, the anti-reflection film 43may be provided as needed. Note that, in the specification, thephotodiode 12, the interconnection layer 20, the color filter 31, andthe microlens 32, which are provided for each pixel in the solid-stateimaging device, are called a solid-state imaging element.

Herein, the photonic crystals 42 will be described. FIGS. 2A and 2B arediagrams schematically illustrating refraction patterns of light in amaterial, in which FIG. 2A illustrates a refraction pattern of light ina material having a positive refraction index and FIG. 2B illustrates arefraction pattern of light in a material having a negative refractionindex. In the drawings, a direction obtained by projecting a travelingdirection of the incident light to the boundary between materials isdefined as an x direction.

As illustrated in FIG. 2A, an optical refraction index of a typicalmaterial 102 is a positive parameter, and in this case the lightgenerally shows a phenomenon in which the light is refracted at theboundary between the materials but travels on an inclined path. That is,when the light is incident on the material 102, for example, at anincident angle θ from the air 101, the light is refracted in thematerial 102 at a refracting angle β and then transmitted from thematerial 102 into the air 103. As a result, assuming that an incidentposition of the light on the material 102 is x₁, the emitting positionx₂ from the material 102 moves on a positive side from the incidentposition x₁ in the x direction. In general, the refraction index will bepositive as long as a naturally-occurring material is concerned.

On the other hand, in recent years, a phenomenon has been known in whichthe material shows a behavior like having the negative refraction indexwhen materials having another refraction index, for example, materialscalled the photonic crystals, are artificially arranged in a cycleshorter than the wavelength (“FDTD Analysis of Wavelength DemultiplexerComposed of Photonic Crystal Superprism and Superlens,” TAKASHIMATSUMOTO, SHINJI FUJITA, and TOSHIHIKO BABA, IEIC Technical Report(Institute of Electronics, Information and Communication Engineers),OPE, Optical Electronics Vol. 105 (No. 142), pp. 47-50, Jun. 17, 2005).When the photonic crystals 104 having such a negative refraction indexare used, the optical path of the light is bent in a reverse directionwith respect to the incident direction of the light in the photoniccrystals 104, as illustrated in FIG. 2B. That is, for example, when thelight is incident on the photonic crystals 104 at the incident angle θfrom the air 101, the light is refracted at the refracting angle −α inthe photonic crystals 104. Furthermore, even when the light istransmitted from the photonic crystals 104 into, for example, the air103, the traveling direction is refracted. In this way, the lightincident on the photonic crystals 104 is refracted in the reversedirection, but turns back to the original direction when it is emittedfrom the photonic crystals 104. As a result, assuming that the incidentposition of the light in the photonic crystals 104 is x₁, the emittingposition x₃ from the photonic crystals 104 moves back on the negativeside (the incident side) from the incident position x₁ in the xdirection.

FIG. 3 is a top view schematically illustrating an exemplary structureof the photonic crystals used in the first embodiment. The photoniccrystals 42 having the above-mentioned negative refraction index areconfigured such that low refraction index materials 422 having arefraction index higher than that of the air (refraction index: 1) arethree-dimensionally and periodically disposed in a high refraction indexmaterial film 421 which has a refraction index higher than that of thelow refraction index material 422. Specifically, the low refractionindex materials 422 having a shape such as a prismatic shape, aspherical shape, a cylindrical shape, or a bowl shape arethree-dimensionally and periodically disposed at vertexes of a cubiclattice or a regular tetrahedron. When the diameter (size) a of the lowrefraction index material 422 in the photonic crystals 42 is 60 to 90nm, and the pitch b of the low refraction index material 422 is 100 to200 nm, the negative refraction index can be achieved with respect tothe light in a visible light range. In addition, with such adisplacement, the photonic crystals are configured to have the samedisplacement when viewed from any direction in a three-dimensionalspace. For example, polysilicon (Si) may be used as the high refractionindex material film 421, and silicon oxide film (SiO₂) or the air may beused as the low refraction index material 422.

The size of the photonic crystals 42 arranged in the pixel (the numberof cycles of the low refraction index materials 422) is represented bythe number of arrangements depending on the pixel size in a directionparallel to the substrate face, and one row (one cycle) or more arearranged in the height direction. With such a structure, the effectillustrated in FIG. 2B can be achieved. However, it is preferable thatthe number of cycles of the low refraction index materials 422 in theheight direction can be adjusted according to a distance for correctingthe positions. In a case where the number of cycles of the lowrefraction index materials 422 in the height direction is set to be 3rows (3 cycles) or more, the position of the light emitted from thephotonic crystals 42 can turn back so as to be incident on thephotodiode 12 of the corresponding pixel.

In addition, the number of the photonic crystals 42 to be disposed onthe outer peripheral side of the pixel forming region R varies dependingon a diameter or a focal length of an actual camera lens. In a practicalspecification, the number of the photonic crystals may be adjusteddepending on the pixel position in the outer peripheral in which theangle increases. In this case, it is ideal for the installation regionof the photonic crystals 42 to be changed based on the diameter, thefocal length, or the like of a camera lens to be used. However, aftermaking the light incident with an inclination by combining the diametersor the focal lengths of actually used camera lenses, a range of pixelsin which the light may be mixed into adjacent pixels is calculated, andthen the installation region of the photonic crystals 42 may be changedbased on a wide range of the pixels on which the light is incident withan inclination. FIGS. 4A and 4B are diagrams illustrating an example ofa region in which the photonic crystals are disposed. As illustrated inFIG. 4A, the photonic crystals 42 (the light incident positioncorrecting layer 40) may be provided in the entire pixel forming regionR and as illustrated in FIG. 4B, the pixel forming region R is dividedinto 9 regions and the photonic crystals 42 may be provided in regionsRa among the divided regions except the center region Rb.

Furthermore, the cyclic structures of the photonic crystals 42 may beconstant in one pixel forming region R, or may be different from eachother in every region. FIG. 5 is a diagram illustrating an example of amethod of disposing the photonic crystals in the pixel forming region.As illustrated in the drawing, the pixel forming region R is dividedinto a plurality of ring-shaped regions R1 to Rn (n represents a naturalnumber) from the outer peripheral side, and the respective regions arechanged in pitch (or the diameter of the low refraction index material422) of the photonic crystals 42 in the cyclic structure. Generally, theincident angle of the incident light increases as the region comes tonear the outer peripheral portion of the pixel forming region R. Forexample, the region R1 of the outer peripheral portion is configured tomake the pitch of the low refraction index materials 422 of the photoniccrystals 42 have P1; the region R2 adjacent to the inside of the regionR1 is configured to make the pitch of the low refraction index materials422 of the photonic crystals 42 have P2; and so on, and the region Rnadjacent to the inside of the region Rn−1 is configured to make thepitch of the low refraction index materials 422 of the photonic crystals42 have Pn. Then, with the configuration in which a difference betweenthe incident position of the light to the photonic crystals 42 and theemitting position of the light from the photonic crystals 42 is made tobe large as the region comes to near the region R1 of the outerperipheral portion from the region Rn, it is possible to correct theposition of the incident light according to the incident angle of theincident light.

Further, the photonic crystals 42 used in the embodiment is configuredsuch that the low refraction index materials 422 formed in apredetermined size are three-dimensionally and periodically disposed inthe high refraction index material film 421, but no line defect or pointdefect is introduced in the cyclic structure. Namely, it is not the casewhere the photonic crystals which constitute wave guides are used by theintroduction of a line-shape defect or the like to thethree-dimensionally cyclic structure, but the case where the photoniccrystals 42 are used which include the negative refraction index only inthe three-dimensionally cyclic structure without defective structure.

FIGS. 6A to 6C are diagrams illustrating calculation results of opticalsimulations in which an optical path of the photonic crystals having anegative refraction index is simulated. For example, in a case where thephotonic crystals 42 are formed in the high refraction index materialfilm 421 having the refraction index 3 such that the low refractionindex materials 422, which have a diameter of 75 nm and a refractionindex of 1.45, are stacked by three cycles in a cubic lattice shape at apitch of 150 nm, FIG. 6A is a diagram illustrating an optical path in acase of incidence of the light having a wavelength of 430 nm on thephotonic crystals 42; FIG. 6B is a diagram illustrating the optical pathin a case of incidence of the light having a wavelength of 530 nm; andFIG. 6C is a diagram illustrating the optical path in a case ofincidence of the light having a wavelength of 630 nm. As illustrated inthe drawing, the photonic crystals 42 make the optical path of even anylight beam, corresponding to a color B, G, or R, refracted to the samedirection, and thus it is possible to make the emitting position fromthe photonic crystals 42 turning back to the incident direction of thelight. Provided that, in the case of this photonic crystals 42, theeffect is boosted as the wavelength becomes shorter.

FIGS. 7A to 7C are diagrams schematically illustrating an operation ofthe solid-state imaging device according to the embodiment, in whichFIG. 7A is a cross-sectional view illustrating the entire solid-stateimaging device, FIG. 7B is a cross-sectional view illustrating a pixelon an outer peripheral portion near the photonic crystals, and FIG. 7Cis a cross-sectional view illustrating a conventional case in which apixel on the outer peripheral portion has no photonic crystals. Asillustrated in FIG. 7A, the light is incident on the pixel near thecenter of the pixel forming region R of the solid-state imaging devicein a direction perpendicular to the substrate as depicted by an opticalpath Lb. However, the light is incident on the pixel near the outerperipheral portion of the pixel forming region R in an inclineddirection with respect to the direction perpendicular to the substrateas depicted by an optical path La.

FIG. 7C illustrates the optical path in the pixel of the outerperipheral portion in a case where there is no photonic crystals 42. Asdepicted by an optical path Lc in the drawing, since the microlens 32,the color filter 31, the interconnection layer 20 (the interlayerinsulating film 22) each have positive refraction indexes, when thelight is incident on the substrate face in an inclined direction, thelight transmitted through the color filter 31 will slip out to theadjacent pixel before the light reaches a light-receiving unit (thephotodiode 12).

On the other hand, as depicted by the optical path La in FIG. 7B, thephotonic crystals 42 having the negative refraction index is disposed inthe outer peripheral portion of the pixel forming region R. Therefore,the light incident with an inclination turns to a direction, opposite tothe direction in which the light has been incident, at the boundarybetween the color filter 31 (the anti-reflection film 43) and thephotonic crystals 42. Then, the light turns once more to the direction,in which the light has been incident, at the boundary between thephotonic crystals 42 and the anti-reflection film 41. In this way, theposition of the light emitted from the photonic crystals 42 is correctedso as to make the light turn back to the incident direction. As aresult, while the occurrence of color mixing is suppressed from thepixel in the outer peripheral portion of the pixel forming region R, thelight is easily introduced to the photodiode 12.

Next, a method of manufacturing the solid-state imaging device havingsuch a structure will be described. FIGS. 8A to 8F are cross-sectionalviews schematically illustrating an example of procedures performed in amethod of manufacturing the solid-state imaging device according to thefirst embodiment. FIG. 9 is a top view of FIG. 8B. Further, since amethod of manufacturing portions other than the photonic crystals 42 isthe same as that in the conventional solid-state imaging device, thedescription herein will be made only for the method of manufacturing thephotonic crystals 42.

First, similarly to the conventional solid-state imaging device, thephotodiodes are two-dimensionally disposed above the substrate;peripheral circuits and the like are formed; and the interconnectionsare formed thereon through the interlayer insulating film 22. Then, asillustrated in FIG. 8A, the anti-reflection film 41, a high refractionindex material film 421 a, and a low refraction index material film 422a are sequentially stacked on the interlayer insulating film 22. Forexample, a SiO₂ film and the like may be used as the interlayerinsulating film 22, a SiN film may be used as the anti-reflection film41, a poly-Si film having a thickness of 75 nm may be used as the highrefraction index material film 421 a, and a SiO₂ film having a thicknessof 75 nm may be used as the low refraction index material film 422 a.

A resist (not illustrated) is coated on the low refraction indexmaterial film 422 a, and cylindrical patterns having a diameter of 75 nmare disposed at a pitch of 150 nm through a lithography technique to bein a tetragonal lattice shape in the pixel region which includes pixelsin the outer peripheral portion of the pixel forming region. At thistime, the resist is not disposed in a region where the photonic crystals42 are not formed. Note that, herein, the pattern shape is a cylindricalshape, but may be a rectangular shape or a spherical shape. In addition,the diameter of the pattern may be in a range from 50 to 100 nm, and thepitch of the pattern may be in a range from 100 to 200 nm. Furthermore,as for a displacement method, the patterns may be formed in atwo-dimensionally cyclic structure, or may be disposed to be positionedon vertexes of triangle lattices.

Thereafter, as illustrated in FIGS. 8B and 9, the low refraction indexmaterial film 422 a is etched using the patterned resist as a maskthrough an anisotropic etching technique such as an RIE (Reactive IonEtching) method. Therefore, cylindrical pillars made of the lowrefraction index material film 422 a are formed in the region havingformed with the photonic crystals 42, and the low refraction indexmaterial film 422 a is removed from the region having formed no photoniccrystals 42.

After the removal of the resist, as illustrated in FIG. 8C, a highrefraction index material film 421 b is formed with a predeterminedthickness above the entire surface of the substrate 11. For example, thepoly-Si film having a thickness of 75 nm may be used as the highrefraction index material film 421 b. Thereafter, by repeatedlyperforming the processes illustrated in FIGS. 8B and 8C by apredetermined number of times, as illustrated in FIG. 8D, the regionhaving formed the photonic crystals 42 is formed such that the photoniccrystals 42 are obtained in which the low refraction index materialfilms 422 a to 422 c having the cylindrical shape in the high refractionindex material films 421 a to 421 d are arranged three-dimensionally andperiodically, and the region having formed no photonic crystals 42 isformed such that the high refraction index material films 421 a to 421 dare formed in a predetermined thickness.

The resist (not illustrated) is coated above the entire surface of thesubstrate 11, and patterned such that only the region having formed thephotonic crystals 42 is coated by the resist. The region having formedthe photonic crystals 42 is a region including at least the outerperipheral portion of the pixel forming region as described above.Thereafter, the anisotropic etching technique such as the RIE method isemployed to perform an etching process using the patterned resist as amask, so that the high refraction index material films 421 a to 421 d inthe region having formed with no photonic crystals 42 are removed. Afterthe removal of the resist, as illustrated in FIG. 8E, theanti-reflection film 43 and the protection film 51 are formed above theentire surface of the substrate 11. The anti-reflection film 43 may bemade of a material having a lower refraction index compared with thephotonic crystals 42, for example, a SiN film or the like. In addition,the protection film 51 is formed to protect the photonic crystals 42when the interlayer insulating film 23 filled in the region havingformed no photonic crystals 42 is planarized.

As illustrated in FIG. 8F, the interlayer insulating film 23 is formedabove the entire surface of the substrate 11 such that the top facethereof is higher than that of the protection film 51 in the regionhaving formed the photonic crystals 42. Then, while the interlayerinsulating film 23 is removed until the protection film 51 is exposedfrom the region having formed the photonic crystals 42 through a CMP(Chemical Mechanical Polishing) method, the top face of the interlayerinsulating film 23 is planarized. Thereafter, similarly to theconventional method of manufacturing the solid-state imaging device, thecolor filter 31 is disposed above each pixel region R_(p), and furtherthe microlens 32 is disposed on the color filter 31, thereby obtainingthe solid-state imaging device illustrated in FIG. 1.

According to the first embodiment, since the photonic crystals 42 havingthe three-dimensionally cyclic structure is disposed in a layer underthe color filter 31 of the pixel in the region including the outerperipheral portion of the pixel forming region R, the position of thelight to be emitted from the photonic crystals 42 can turn to theincident direction of the light. As a result, even the light incidentwith an inclination is prevented from being incident on the adjacentpixel before reaching the photodiode 12, and the influence of cross talkon the pixel in the outer peripheral portion of the pixel forming regionR can be reduced compared with the related art. In addition, even if theangle of a principal ray incident on the pixel in the outer peripheralportion of the pixel forming region R increases, it is possible toprevent the sensitivity of the image quality from being degraded due tothe loss in light condensing.

Second Embodiment

FIGS. 10A to 10H are cross-sectional views illustrating an example ofprocedures performed in a method of manufacturing a solid-state imagingdevice according to a second embodiment. FIG. 11 is a top view of FIG.10B. Since the method of manufacturing portions other than the photoniccrystals 42 is the same as that in the conventional solid-state imagingdevice, the second embodiment will be described only for the method ofmanufacturing the photonic crystals 42.

First, as illustrated in FIG. 10A, the photodiodes are two-dimensionallydisposed; the interlayer insulating film 22 is formed above thesubstrate in which peripheral circuits and the like are formed; andfurther the anti-reflection film 41 and the high refraction indexmaterial film 421 a are sequentially stacked thereon. For example, aSiO₂ film and the like may be used as the interlayer insulating film 22,a SiN film may be used as the anti-reflection film 41, and a poly-Sifilm having a thickness of 150 nm may be used as the high refractionindex material film 421 a.

A resist (not illustrated) is coated on the high refraction indexmaterial film 421 a, and cylindrical holes having a diameter of 75 nmare disposed at a pitch of 150 nm through a lithography technique so asto be in a tetragonal lattice shape in the resist region which includespixels in the outer peripheral portion of the pixel forming region R. Atthat time, the resist is not disposed in a region where the photoniccrystals 42 are not formed. Note that, herein, the pattern shape is acylindrical shape, but may be a rectangular shape or a spherical shape.In addition, the diameter of the hole may be in a range from 50 to 100nm, and the pitch of the pattern may be in a range from 100 to 200 nm.Furthermore, as for a method of disposing the holes, the holes may beformed in the two-dimensionally cyclic structure, or may be disposed tobe positioned on vertexes of triangle lattices.

Thereafter, as illustrated in FIGS. 10B and 11, the high refractionindex material film 421 a is etched using the patterned resist as a maskthrough the anisotropic etching technique such as the RIE method to thedepth in which the high refraction index material film 421 a is notpassed through. For example, the etching is performed to the halfthickness (in this case, 75 nm) of the high refraction index materialfilm 421 a. Therefore, the region having formed the photonic crystals 42is formed such that the cylindrical holes 425 are formed in thetwo-dimensionally cyclic structure in the high refraction index materialfilm 421 a, and the region having formed no photonic crystals 42 isformed such that the high refraction index material film 421 a having apredetermined thickness is removed.

After the removal of the resist, as illustrated in FIG. 10C, the lowrefraction index material film 422 a is formed above the entire surfaceof the patterned high refraction index material film 421 a such that thelow refraction index material film 422 a fills the formed cylindricalholes 425 enough to be higher than the top face of the high refractionindex material film 421 a in the region having formed the photoniccrystals 42. Thereafter, as illustrated in FIG. 10D, the low refractionindex material film 422 a which is formed to be higher than the highrefraction index material film 421 a is removed through the CMP methodor the like. For example, the SiO₂ film may be used as the lowrefraction index material film 422 a.

As illustrated in FIG. 10E, the high refraction index material film 421b is formed by a predetermined thickness above the entire surface of thesubstrate 11. For example, the poly-Si film having a thickness of 150 nmmay be used as the high refraction index material film 421 b.Thereafter, by repeatedly performing the processes illustrated in FIG.10B to 10E by a predetermined number of times, as illustrated in FIG.10F, the region having formed the photonic crystals 42 is formed suchthat the photonic crystals 42 are obtained in which the low refractionindex material films 422 a to 422 c having the cylindrical shape arearranged three-dimensionally and periodically, and the region havingformed no photonic crystals 42 is formed of a stacked film in which thehigh refraction index material films 421 a to 421 d and the lowrefraction index material films 422 a to 422 c are alternativelystacked.

As illustrated in FIG. 10G, the resist (not illustrated) is coated abovethe entire surface of the substrate 11, and patterned such that only theregion having formed the photonic crystals 42 is coated by the resist.Thereafter, the anisotropic etching technique such as the RIE method isemployed to perform an etching process using the patterned resist as amask, so that the stacked film including the high refraction indexmaterial films 421 a to 421 d and the low refraction index materialfilms 422 a to 422 c in the region having formed no photonic crystals 42is removed. After the removal of the resist, the anti-reflection film 43and the protection film 51 are formed above the entire surface of thesubstrate. The anti-reflection film 43 may be made of a material havinga lower refraction index compared with the photonic crystals 42, forexample, a SiN film or the like. In addition, the protection film 51 isformed to protect the photonic crystals 42 when the interlayerinsulating film 23 filled in the region having formed no photoniccrystals 42 is planarized.

As illustrated in FIG. 10H, the interlayer insulating film 23 is formedabove the entire surface of the substrate 11, and then while theinterlayer insulating film 23 is removed until the protection film 51 isexposed from the region having formed the photonic crystals 42 throughthe CMP method, the top face of the interlayer insulating film 23 isplanarized. Thereafter, similarly to the conventional method ofmanufacturing the solid-state imaging device, the color filter 31 isdisposed on each pixel region R_(P), and further the microlens 32 isdisposed on the color filter 31, thereby obtaining the solid-stateimaging device illustrated in FIG. 1.

FIGS. 12A to 12C are cross-sectional views schematically illustrating anexample of procedures performed in a method of manufacturing thesolid-state imaging device in a case where the low refractive indexmaterial is the air. In a case where the low refraction index materialof the photonic crystals 42 is the air, after the process illustrated inFIG. 10B, a high refraction index material film 421 b-1 is formed on thehigh refraction index material film 421 a having patterned with theholes 425 using a film formation method having poor fillingcharacteristics as illustrated in FIG. 12A. The formed high refractionindex material film 421 b-1 is constructed such that valleys are formedat positions of the holes 425, and peaks in the region having formed thehigh refraction index material film 421 b-1. In this way, the holes 425are covered to form bowl-shaped spaces 425 a. The spaces 425 a, forexample, contain the air (having a refraction index of 1).

As illustrated in FIG. 12B, a high refraction index material film 421b-2 is formed by a predetermined thickness on the high refraction indexmaterial film 421 b-1. Then, the patterning is performed through thelithographic technique and the etching technique such that thecylindrical holes 425 having a predetermined size are two-dimensionallydisposed in a predetermined cycle in the pixel region including thepixels in the outer peripheral portion of the pixel forming region R.

Thereafter, by repeatedly performing the processes illustrated in FIGS.12A and 12B by a predetermined number of times, as illustrated in FIG.12C, the region having formed the photonic crystals 42 is formed suchthat the photonic crystals 42 is obtained in which bowl-shaped spaces425 a to 425 c are arranged three-dimensionally and periodically, andthe region having formed no photonic crystals 42 is formed of a stackedfilm of the high refraction index material films 421 a to 421 d. Here,the low refraction index material 422 is configured of the spaces 425 ato 425 c. Then, the same processes illustrated in FIG. 10G and thesubsequent drawings are performed, thereby manufacturing the solid-stateimaging device.

According to the second embodiment, the solid-state imaging devicehaving the structure illustrated in the first embodiment can also bemanufactured. In addition, in the second embodiment, the holes 425formed two-dimensionally and periodically in the high refraction indexmaterial film 421 are not filled with something else, and the upperportion is covered, so that the air can be contained in the spaces 425 ato 425 c. As a result, since the air having a refraction index of 1 canbe used as the low refraction index material 422, the photonic crystals42 having a great refraction index difference can be used.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A solid-state imaging device comprising: aphotodiode which is in a pixel region in which each of a plurality ofpixels is disposed, the pixels being formed in a pixel forming regionabove a substrate in a matrix shape; an interconnection layer comprisinginterconnections to connect the photodiode to peripheral circuits formedabove the substrate and an interlayer insulating film to insulate theinterconnections from each other, wherein the interconnection layer isabove the photodiode; and a filter which is above the interconnectionlayer corresponding to the pixel region, wherein the filter limits awavelength of light incident on the photodiode, wherein a light incidentposition correcting layer is between the filter corresponding to thepixel disposed in at least the outer peripheral portion of the pixelforming region and the interconnection layer, the light incidentposition correcting layer comprising an anti-reflection film which isabove the interconnection layer and materials which have a negativerefraction index and is above the anti-reflection film, and the pixelwithout the light incident position correcting layer comprising thematerials which have the negative refraction index is disposed in acenter portion of the pixel forming region.
 2. The solid-state imagingdevice according to claim 1, wherein the materials having the negativerefraction index are photonic crystals which have a refraction index of1 or higher, and in which low refraction index materials having arefraction index equal to or less than that of the interlayer insulatingfilms are disposed in a three-dimensionally cyclic structure in a highrefraction index material film having a refraction index higher than theinterlayer insulating films and the low refraction index materials. 3.The solid-state imaging device according to claim 2, wherein thephotonic crystals is configured such that the low refraction indexmaterials are disposed in a cubic lattice shape or a tetrahedral latticeshape in the high refraction index material film.
 4. The solid-stateimaging device according to claim 3, wherein the low refraction indexmaterials are 60 to 90 nm in size and disposed at a pitch of 100 to 200nm.
 5. The solid-state imaging device according to claim 4, wherein thesize and the pitch of the low refraction index materials are constant inone pixel region in which the light incident position correcting layeris provided.
 6. The solid-state imaging device according to claim 4,wherein the size or the pitch of the low refraction index materials isset to a different value according to a distance from the outerperipheral portion of the pixel forming region with the pixel region asa unit.
 7. The solid-state imaging device according to claim 6, whereinthe size or the pitch of the low refraction index materials is set suchthat an absolute value of a difference between an emitting position oflight from the photonic crystals and an incident position of light tothe photonic crystals increases as the pixel region comes to near theouter peripheral portion of the pixel forming region.
 8. The solid-stateimaging device according to claim 2, wherein the interlayer insulatingfilm is a material based on SiO₂, the low refraction index material is amaterial based on SiO₂ or air, and the high refraction index materialfilm is a material based on Si.
 9. A method of manufacturing asolid-state imaging device, the method comprising: forming photodiodesabove a substrate in a matrix shape; forming an interconnection layerabove the substrate, the interconnection layer comprisinginterconnections to connect the photodiode to peripheral circuits formedabove the substrate and a first interlayer insulating film to insulatethe interconnections; forming sequentially a first anti-reflection filmabove the interconnection layer and a first high refraction indexmaterial film having a first refraction index; forming a low refractionindex material film on the first high refraction index material film,the low refraction index material film having a second refraction indexwhich is lower than the first refraction index and a refraction index ofthe first interlayer insulating film and equal to or greater than 1;etching the low refraction index material film in an island shape sothat a two-dimensionally cyclic structure portion which has atwo-dimensionally cyclic structure is formed in a region correspondingto the photodiode disposed in at least an outer peripheral portion ofthe pixel forming region in which the photodiodes are formed in a matrixshape, and the two-dimensionally cyclic structure portion is not formedin a region corresponding to the photodiode disposed in a center portionof the pixel forming region; forming a second high refraction indexmaterial film having the first refraction index on the first highrefraction index material film on which the two-dimensionally cyclicstructure portion is formed, the second high refraction index materialfilm becoming thicker than a thickness of the low refraction indexmaterial film; removing the first and the second high refraction indexmaterial films in the center portion of the pixel forming region;filling a second interlayer insulating film in the center portion of thepixel forming region; and forming a filter which limits a wavelength oflight incident on the photodiode above the second interlayer insulatingfilm corresponding to the region in which the photodiodes are formedrespectively.
 10. The method of manufacturing the solid-state imagingdevice according to claim 9, further comprising, after the removing ofthe first and the second high refraction index material films and beforethe filling of the second interlayer insulating film, forming a secondanti-reflection film above the second high refraction index materialfilm.
 11. The method of manufacturing the solid-state imaging deviceaccording to claim 9, further comprising, after the removing of thefirst and the second high refraction index material films and before thefilling of the second interlayer insulating film, forming a protectionfilm above the second high refraction index material film, wherein inthe filling of the second interlayer insulating film, the secondinterlayer insulating film is removed using the protection film as astopper.
 12. The method of manufacturing the solid-state imaging deviceaccording to claim 9, wherein the processes from the forming of the lowrefraction index material film to the forming of the second highrefraction index material film are repeatedly performed by apredetermined number of times to form a three-dimensionally cyclicstructure portion in which a plurality of the two-dimensionally cyclicstructure portions are stacked in a height direction.
 13. The method ofmanufacturing the solid-state imaging device according to claim 12,wherein in the forming of the two-dimensionally cyclic structureportion, the low refraction index materials are disposed such that thethree-dimensionally cyclic structure portion is formed in a cubiclattice shape or a tetrahedral lattice shape.
 14. The method ofmanufacturing the solid-state imaging device according to claim 9,wherein in the forming of the two-dimensionally cyclic structureportion, the two-dimensionally cyclic structure portion is formed suchthat the low refraction index materials with a size of 60 to 90 nm aredisposed at a pitch of 100 to 200 nm.
 15. The method of manufacturingthe solid-state imaging device according to claim 14, wherein in theforming of the two-dimensionally cyclic structure portion, the size orthe pitch of the low refraction index materials is set to a differentvalue according to a distance from the outer peripheral portion of thepixel forming region with the pixel region as a unit.